One-step process for the preparation of alkenyl succinic anhydride

ABSTRACT

A process for the preparation of an alkenyl-substituted succinic anhydride wherein the alkenyl substituent has a number average molecular weight of from about 500 to 5000 and the average number of succinic groups per alkenyl group is greater than 1.2 which comprises reacting a polyolefin having an alkylvinylidene isomer content of less than about 10 percent and a number average molecular weight of about 500 to 5000 with maleic anhydride in the presence of a free radical initiator at a temperature in the range of about 80° C. to 220° C. for a period of less than 20 hours, wherein the molar ratio of maleic anhydride to polyolefin is about 1.0:1 to 9:1, and wherein the half-life of the decomposition of the free radical initiator is about 5 minutes to 10 hours at the reaction temperature.

BACKGROUND OF THE INVENTION

The present invention relates to a process for preparing compositionswhich are useful as intermediates for dispersants used in lubricatingoil compositions or as dispersants themselves. In addition, some of thecompositions prepared by the present process are useful in thepreparation of high molecular weight dispersants which have superiordispersant properties for dispersing sludge and varnish. Such highmolecular weight dispersants also advantageously impart fluiditymodifying properties to lubricating oil compositions which aresufficient to allow elimination of some proportion of viscosity indeximprover from multigrade lubricating oil compositions which containthese dispersants.

It is known in the art that alkenyl-substituted succinic anhydrides havebeen used as dispersants. Such alkenyl-substituted succinic anhydrideshave been prepared by two different processes, a thermal process (see,e.g., U.S. Pat. No. 3,361,673) and a chlorination process (see e.g.,U.S. Pat. No. 3,172,892). The polyisobutenyl succinic anhydride("PIBSA") produced by the thermal process has been characterized as amonomer containing a double bond in the product. Although the exactstructure of chlorination PIBSA has not been definitively determined,the chlorination process PIBSA materials have been characterized asmonomers containing either a double bond, a ring other than succinicanhydride ring and/or chlorine in the product. [(See J. Weill and B.Sillion, "Reaction of Chlorinated Polyisobutene with Maleic Anhydride:Mechanism Catalysis by Dichloramaleic Anhydride", Revue de l'InstitutFrancais du Petrole, Vol. 40, No. 1, pp. 77-89 (January-February,1985).]Such compositions include one-to-one monomeric adducts (see,e.g., U.S. Pat. Nos. 3,219,666; 3,381,022) as well as adducts havingpolyalkenyl-derived substituents adducted with at least 1.3 succinicgroups per polyalkenyl-derived substituent (see, e.g., U.S. Pat. No.4,234,435).

Commonly assigned International Patent Application No. PCT/US89/04270,Publication No. WO 90/03359, dated Apr. 5, 1990 and entitled "NovelPolymeric Dispersants Having Alternating Polyalkylene and SuccinicGroups" discloses copolymers prepared by reacting an unsaturated acidicreactant, such as maleic anhydride, with a high molecular weight olefin,such as polyisobutene, in the presence of a free radical initiator,wherein at least about 20 percent of the total high molecular weightolefin comprises an alkylvinylidene isomer and wherein the highmolecular weight olefin has a sufficient number of carbon atoms suchthat the resulting copolymer is soluble in lubricating oil.

U.S. Pat. No. 4,234,435 to Meinhardt et al., assigned to The LubrizolCorporation, discloses substituted succinic acylating agents derivedfrom polyalkenes, such as polybutene, and a dibasic carboxylic reactant,such as maleic acid or anhydride, wherein the polyalkenes have a numberaverage molecular weight of about 1300 to 5000 and a ratio of weightaverage to number average molecular weight of about 1.5 to 4. Theseacylating agents are further characterized by the presence of an averageof at least 1.3 succinic groups for each equivalent weight ofsubstituent group. Meinhardt et al. teach that such acylating agents areprepared by heating the polyalkene and carboxylic reactant with chlorinein a one-step process or, alternatively, by first reacting thepolyalkene with chlorine and then reacting the resulting chlorinatedpolyalkene with the carboxylic reactant. This patent further teachesthat such substituted succinic acylating agents and their derivativesare useful lubricating oil dispersant additives which also exhibitviscosity index improving properties.

U.S. Pat. No. 4,873,004 to Beverwijk et al., assigned to Shell OilCompany, discloses an alkyl or alkenyl-substituted succinic anhydride,wherein the alkyl or alkenyl group on the anhydride has a number averagemolecular weight of from 600 to 1300 and wherein the average number ofsuccinic groups per alkyl or alkenyl group is between 1.4 and 4.0.Beverwijk et al. teach that these alkyl or alkenyl-substituted succinicanhydrides can be prepared by mixing a polyolefin with maleic anhydrideand passing chlorine through the mixture, or by reacting a chlorinatedpolyolefin with maleic anhydride. Beverwijk et. al. further teach thatthe succinimide derivatives of such substituted succinic anhydrides areuseful dispersant additives for lubricating oils.

U.S. Pat. No. 3,367,864 to Elliot et al., assigned to Castrol Limited,discloses in Example I thereof the preparation of a polyisobutenylsuccinic anhydride by the reaction of about a 1:1 molar ratio ofpolyisobutylene and maleic anhydride in refluxing toluene and in thepresence of a di-tertiary-butyl peroxide free radical initiator. Elliotet al. further teach that the succinic anhydride product produced bythis method is similar to the product obtained by thermally reactingpolyisobutylene and maleic anhydride at 240° C. for 30 hours.

It has generally been recognized in the art that the polyisobutenylsuccinic anhydride prepared by employing a conventional thermal processis primarily a monomeric one-to-one adduct, that is, having about onesuccinic group per polyisobutenyl group in the product. However, recentanalysis of a number of polyisobutenyl succinic anhydride productsproduced by following the free radical-initiated process of Example I ofU.S. Pat. No. 3,367,864 has resulted in a finding that such products aremonomeric adducts containing an average of about 1.6 or greater succinicgroups per polyisobutenyl group.

Moreover, European Patent Application Publication No. 0,355,895 A2,published Feb. 28, 1990, discloses a process for the preparation ofpolyolefin-substituted succinic anhydrides in which the average molarratio of succinic groups to polyolefin chains is greater than 1.3 to 1,which comprises heating a polyolefin with at least a molar excess ofmaleic anhydride, wherein the polyolefin employed contains at least 70percent of the terminal groupings in a structure having an alphaolefinic bond or structures in equilibrium with such alpha olefinicstructures. Thus, this European patent application teaches that greaterthan 1.3 succinic groups per polyolefin group can be obtained when thepolyolefin employed is one wherein the predominant isomer is analkylvinylidene.

SUMMARY OF THE INVENTION

The present invention is directed to a one-step process for thepreparation of an alkenyl-substituted succinic anhydride wherein thealkenyl substituent has a number average molecular weight of from about500 to 5000 and the average number of succinic groups per alkenyl groupis greater than 1.2 which comprises reacting a polyolefin having analkylvinylidene isomer content of less than about 10 percent and anumber average molecular weight of about 500 to 5000 with maleicanhydride in the presence of a free radical initiator at a temperaturein the range of about 80° C. to 220° C. for a period of less than 20hours, wherein the molar ratio of maleic anhydride to polyolefin isabout 1.0:1 to 9:1, and wherein the half-life of the decomposition ofthe free radical initiator is about 5 minutes to 10 hours at thereaction temperature.

Among other factors, the present invention is based on the discoverythat certain alkenyl-substituted succinic anhydrides containing anaverage of greater than 1.2 succinic groups per alkenyl group can beeffectively prepared in high yields and conversions at shorter reactiontimes by employing a unique one-step process which does not involve theuse of chlorine, thereby resulting in a product having improvedenvironmental properties.

The average number of succinic groups per alkenyl group in the alkenylsuccinic anhydride produced by the present process is greater than 1.2,preferably at least about 1.3, more preferably from about 1.3 to 4.0,and most preferably from about 1.3 to about 2.5.

Suitable polyolefins for use in preparing the alkenyl succinic anhydrideproducts will have a number average molecular weight of about 500 to5000, preferably from about 700 to 3000, and more preferably, from about900 to 2500. Generally, such polyolefins will contain at least about 35carbon atoms, preferably about 50 carbon atoms or greater. Preferredpolyolefins are polybutene and polypropylene, particularlypolyisobutene. Suitable polyolefins will also contain an alkylvinylideneisomer content of less than about 10 percent.

The succinic anhydride products prepared by the process of the inventionare useful as dispersants themselves and also as intermediates in thepreparation of other dispersant additives having improved dispersancyand/or detergency properties when employed in a lubricating oil.

The products produced by the instant process can also be used to formpolysuccinimides which are prepared by reacting the alkenyl succinicanhydride with a polyamine to give a polysuccinimide. Thesepolysuccinimides are useful as dispersants and/or detergents in fuelsand oils. In addition, these polysuccinimides have advantageousviscosity modifying properties, and may provide a viscosity index credit("V.I. Credit") when used in lubricating oils, which may permitelimination of some portion of viscosity index improver ("V.I.Improver") from multigrade lubricating oils containing the same.

Moreover, the succinic anhydrides prepared by the present process can beemployed to make modified polysuccinimides wherein one or more of thenitrogens of the polyamine component is substituted with a hydrocarbyloxycarbonyl, a hydroxyhydrocarbyl oxycarbonyl or a hydroxypoly(oxyalkylene)-oxycarbonyl. These modified polysuccinimides areimproved dispersants and/or detergents for use in fuels or oils.

Accordingly, the alkenyl succinic anhydrides made by the present processare useful in providing a lubricating oil composition comprising a majoramount of an oil of lubricating viscosity and an amount of a succinicanhydride, polysuccinimide or modified succinimide additive sufficientto provide dispersancy and/or detergency. These additives may also beformulated in lubricating oil concentrates which contain about 10 toabout 50 weight percent of the additive.

Furthermore, the alkenyl succinic anhydrides formed by the presentprocess can be used to provide a fuel composition comprising a majorportion of a fuel boiling in a gasoline or diesel range and an amount ofsuccinic anhydride, polysuccinimide or modified succinimide additivesufficient to provide dispersancy and/or detergency. These additives canalso be used to make fuel concentrates comprising an inert stableoleophilic organic solvent boiling in the range of about 150° F. toabout 400° F. and from about 5 to about 50 weight percent of suchadditive.

DETAILED DESCRIPTION OF THE INVENTION

The high molecular weight polyolefins used in the preparation of theinstant alkenyl succinic anhydrides are of sufficiently long chainlength so that the resulting composition is soluble in and compatiblewith mineral oils, fuels and the like. Thus, the polyolefin willtypically contain about 35 carbon atoms or greater, preferably about 50carbon atoms or greater.

Such high molecular weight polyolefins are generally mixtures ofmolecules having different molecular weights and can have at least onebranch per 6 carbon atoms along the chain, preferably at least onebranch per 4 carbon atoms along the chain, and move preferably about onebranch per 2 carbon atoms along the chain. These branched chain olefinsmay conveniently comprise polyalkenes prepared by the polymerization ofolefins of from 3 to 6 carbon atoms, and preferably from olefins of from3 to 4 carbon atoms, and more preferably from propylene or isobutylene.The addition-polymerizable olefins employed are normally 1-olefins. Thebranch may be of from 1 to 4 carbon atoms, more usually of from 1 to 2carbon atoms and preferably methyl.

The polyolefins employed in the process of the present invention may beprepared by conventional techniques well known in the art, such asaluminum chloride-catalyzed polymerization of lower olefins.

Preferred polyolefins are polyisobutenes having number average molecularweights of about 500 to about 5000, more preferably about 700 to about3000. Especially preferred are those polyisobutenes having numberaverage molecular weights of about 900 to 2500.

The polyolefins employed in the instant process will also have a lowalkylvinylidene isomer content, that is, less than about 10 percentalkylvinylidene. As used herein, the term "alkylvinylidene" or"alkylvinylidene isomer" is meant to indicate olefins having theformula: ##STR1## wherein R₁ is lower alkyl of 1 to about 6 carbon atomsand R₂ is a polyolefin residue. Consequently, high alkylvinylidenepolyolefins having greater than about a 10 percent alkylvinylidenecontent, such as the commercially available Ultravis type ofpolyisobutene, are unsuitable for use in the process of the presentinvention, since such materials tend to form copolymers with maleicanhydride in the presence of a free radical initiator.

In general, the ratio of Weight average molecular weight (M_(W)) tonumber average molecular weight (M_(N)), that is, M_(W) /M_(N), for thepolyolefins employed in the present invention will fall within the rangeof about 1.1 to 4.0. The M_(W) and M_(N) values for the polyolefins usedin this invention are determined by gel permeation chromatography (GPC)as described, for example, in U.S. Pat. No. 4,234,435 to Meinhardt etal.

As noted above, the present invention relates to a unique one-stepprocess for preparing an alkenyl succinic anhydride having greater than1.2 succinic groups per alkenyl group, which involves reacting apolyolefin with maleic anhydride in the presence of a free radicalinitiator to give an alkenyl succinic anhydride having an average ofgreater than 1.2 succinic groups per alkenyl group.

Accordingly, in the process of the instant invention, the polyolefin andmaleic anhydride are heated in the presence of a free radical initiatorto a temperature in the range of about 80° C. to about 220° C.,preferably about 120° C. to about 180° C., more preferably about 140° C.to about 180° C., and most preferably, about 145° C. to about 165° C.The time of reaction will vary, depending in part upon the reactiontemperature, but will generally be less than 20 hours, preferably about1 to 15 hours. The reaction pressure can be atmospheric, although higherpressures up to about 50 psig are preferred. The molar ratio of maleicanhydride to polyolefin will generally be about 1.0:1 to about 9:1,preferably about 1:5:1 to about 5:1, and more preferably about 2:1 toabout 4:1. Upon completion, this reaction will preferably result ingreater than about a 50 percent conversion of polyolefin to alkenylsuccinic anhydride.

The reaction involved in the present process can be carried out in thepresence or absence of a solvent which is inert to the reaction takingplace. When employed, suitable solvents include toluene, xylene, C₉aromatics, neutral oil, and the like. Preferably, the reaction iscarried out without a solvent.

The alkenyl succinic anhydride produced by the present process willcontain an average of greater than about 1.2 succinic groups per alkenylgroup, preferably at least about 1.3, more preferably from about 1.3 to4.0, and most preferably about 1.3 to 2.5 succinic groups per alkenylgroup.

In general, the process of the present invention can be initiated by anyfree radical initiator. Such initiators are well known in the art.However, the choice of free radical initiator may be influenced by thereaction temperature employed.

It has now been found that if the half-life of the decomposition of thefree radical initiator at the temperature of reaction is in the range ofabout 5 minutes to 10 hours, preferably about 10 minutes to 5 hours, andmore preferably about 10 minutes to 2 hours, then the desired alkenylsuccinic anhydride product can be effectively prepared in high yieldsand conversions at short reaction times.

The preferred free-radical initiators are the peroxide-type initiatorsand azo-type initiators.

The peroxide-type free-radical initiator can be organic or inorganic,the organic having the general formula: R₃ OOR₃ ' where R₃ is anyorganic radical and R₃ ' is selected from the group consisting ofhydrogen and any organic radical. Both R₃ and R₃ ' can be organicradicals, preferably hydrocarbon, aroyl, and acyl radicals, carrying, ifdesired, substituents such as halogens, etc. Preferred peroxides includedi-tert-butyl peroxide, tert-butyl peroxybenzoate, and dicumyl peroxide.

Examples of other suitable peroxides, which in no way are limiting,include benzoyl peroxide; lauroyl peroxide; other tertiary butylperoxides; 2,4-dichlorobenzoyl peroxide; tertiary butyl hydroperoxide;cumene hydroperoxide; diacetyl peroxide; acetyl hydroperoxide;diethylperoxycarbonate; tertiary butyl perbenzoate; and the like.

The azo-type compounds, typified by alpha,alpha'-azo-bisisobutyronitrile (AIBN), are also well-known free-radicalpromoting materials. These azo compounds can be defined as those havingpresent in the molecule the group --N═N wherein the balances aresatisfied by organic radicals, at least one of which is preferablyattached to a tertiary carbon. Other suitable azo compounds include, butare not limited to, p-bromobenzenediazonium fluoborate;p-tolyldiazoamino-benzene; p-bromobenzenediazonium hydroxide; azomethaneand phenyldiazonium halides. A suitable list of azo-type compounds canbe found in U.S. Pat. No. 2,551,813, issued May 8, 1951 to Paul Pinkney.

The half-life values for known free radical initiators at varioustemperatures are readily available from the literature. See, forexample, C. Walling, "Free Radicals in Solution", John Wiley and Sons,Inc., New York (1957). Alternatively, the half-life values are availablefrom the various suppliers of free radical initiators, such as Witco,Atochem, Lucidol, Phillips Petroleum, and the like. Table 1 lists thehalf-life temperatures for a number of free radical initiators at agiven half-life. The half-life temperature is the temperature requiredfor a free radical initiator to exhibit a specified half-life. As arule, the higher the half-life temperature, the lower the half-life ofthe free radical initiator.

                  TABLE 1                                                         ______________________________________                                        HALF-LIFE TEMPERATURES OF VARIOUS FREE                                        RADICAL INITIATORS AT SPECIFIED HALF-LIVES                                               Half-Life Temperature, °C.                                               5       10      2     5     10                                   Initiator    Min.    Min.    Hrs.  Hrs.  Hrs.                                 ______________________________________                                        Dialkyl Peroxides:                                                            di-t-butyl peroxide                                                                        173     166     143   135   129                                  di-t-amyl peroxide                                                                         167     160     137   129   123                                  di-cumyl peroxide                                                                          161     154     131   123   117                                  2, 5-dimethyl-2,                                                                           164     157     134   126   120                                  5-di(t-butylperoxy)                                                           hexane                                                                        Peroxyketals:                                                                 1, 1-di-tannylperoxy-                                                                      134     128     106    99    93                                  cyclohexane                                                                   Diperoxycarbonates:                                                           di-ethylhexylperoxy-                                                                        85      79      60    54    49                                  dicarbonate                                                                   Diacyl Peroxides:                                                             didecanoyl peroxide                                                                        102      96      76    69    64                                  dibenzoyl peroxide                                                                         114     108      86    78    73                                  Peroxy Esters:                                                                t-butyl peroctoate                                                                         115     109      90    82    77                                  t-butyl perbenzoate                                                                        152     144     119   110   104                                  Azo Compounds:                                                                AIBN         105      98      78    72    65                                  ______________________________________                                    

The amount of initiator to employ depends to a large extent on theparticular initiator chosen, the olefin used and the reactionconditions. The initiator should generally be soluble in the reactionmedium. The usual concentrations of initiator are between 0.001:1 and0.4:1 moles of initiator per mole of polyolefin reactant, with preferredamounts between 0.005:1 and 0.20:1.

In carrying out the process of the invention, a single free radicalinitiator or a mixture of free radical initiators may be employed. Forexample, it may be desirable to add an initiator having a lowdecomposition temperature as the mixture is warming to reactiontemperature, and then add an initiator having a higher decompositiontemperature as the mixture reaches higher reaction temperatures.Alternatively, a combination of initiators could both be added prior toheating and reaction. In this case, an initiator having a highdecomposition temperature would initially be inert, but would laterbecome active as the temperature rose.

The initiator may also be added over time. For example, if an initiatoris chosen with a short half-life, e.g., 5-20 minutes, at the reactiontemperature, then the initiator may be added over a period of time sothat an adequate concentration of free radicals will be availablethroughout the reaction period to give improved yields of the desiredproduct.

In general, after the reaction is deemed complete, for example, by NMRanalysis, the reaction mixture is heated to decompose any residualinitiator. For a di(t-butyl) peroxide initiator, this temperature istypically about 160° C. or higher.

As used herein, the term "multiple adduction" refers to the alkenylsuccinic anhydride reaction product of maleic anhydride and polyolefin,wherein more than one molecule of maleic anhydride is bonded to onemolecule of polyolefin.

The average level of multiple adduction can be calculated from thesaponification number (mg KOH per gram of sample) and the activescontent of the alkenyl succinic anhydride product and the molecularweight of the starting polyolefin. By "average level of multipleadduction" is meant the average number of succinic groups per polyolefingroup in the alkenyl succinic anhydride product. For example, an averagemultiple adduction level of 1.0 indicates an average of one succinicgroup per polyolefin group in the alkenyl succinic anhydride product.Likewise, an average multiple adduction level of 1.35 indicates anaverage of 1.35 succinic groups per polyolefin group in the alkenylsuccinic anhydride product, and so forth.

The actives content of the alkenyl succinic anhydride product ismeasured in terms of the actives fraction, wherein an actives fractionof 1.0 is equivalent to 100 percent actives. Accordingly, an activesfraction of 0.5 would correspond to 50 percent actives.

The average level of multiple adduction for the alkenyl succinicanhydride product of maleic anhydride and polyolefin can be calculatedin accordance with the following equation: ##EQU1## whereinP=saponification number of the alkenyl succinic anhydride sample (mgKOH/g)

A=actives fraction of the alkenyl succinic anhydride sample

M_(PO) =number average molecular weight of the starting polyolefin

M_(MA) =molecular weight of maleic anhydride

C=conversion factor=112220 (for conversion of gram-moles of alkenylsuccinic anhydride per gram of sample to milligrams of KOH per gram ofsample)

The saponification number, P, can be measured using known procedures,for example, as described in ASTM D94.

The actives fraction of the alkenyl succinic anhydride can be determinedfrom the percent of unreacted polyolefin according to the followingprocedure. A 5.0 gram sample of the reaction product of maleic anhydrideand polyolefin is dissolved in hexane, placed in a column of 80.0 gramsof silica gel (Davisil 62, a 140 angstrom pore size silica gel), andeluted with 1 liter of hexane. The percent unreacted polyolefin isdetermined by removing the hexane solvent under vacuum from the eluentand weighing the residue. Percent unreacted polyolefin is calculatedaccording to the following formula: ##EQU2##

The weight percent actives for the alkenyl succinic anhydride product iscalculated from the percent unreacted polyolefin using the formula:##EQU3##

The actives fraction of the alkenyl succinic anhydride is thencalculated as follows: ##EQU4## The percent conversion of polyolefin iscalculated from the weight percent actives as follows: ##EQU5## wherein

M_(po) =number average molecular weight of the starting polyolefin

M_(ma) =molecular weight of maleic anhydride

MADD=average level of multiple adduction

It is, of course, understood that alkenyl succinic anhydride productshaving high average levels of multiple adduction, as prepared by theprocess of the present invention, can also be blended with other alkenylsuccinic anhydrides having a lower average level of multiple adduction,for example, a level of around 1.0, to provide an alkenyl succinicanhydride product having an intermediate average level of mutlipleadduction.

The following examples are offered to specifically illustrate thisinvention. These examples and illustrations are not be construed in anyway as limiting the scope of this invention.

EXAMPLES Example 1

1000 grams (0.77 mole) of polyisobutene having a number averagemolecular weight of 1300 and a methylvinylidene isomer content of about6 percent was charged to a reactor and heated to 150° C. and stirred at60 rpm with a mechanical stirrer. To this was added a mixture of 11.2grams (0.077 mole) of di-t-butylperoxide, 120 grams of Chevron 100NRdiluent oil, and a total of 150.90 grams (1.54 moles) of maleicanhydride over a four hour period. Then the reaction was held at 150° C.for an additional one hour. Any unreacted maleic anhydride was removedin vacuo at 190° C. The product was then filtered. The resultingpolyisobutenyl succinic anhydride product had a saponification number of47.7 mg KOH/gram of sample, 31 weight percent actives, and an average ofabout 2.06 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 28.0 percent. The half-life of thedi-t-butylperoxide free radical initiator at the reaction temperature of150° C. is about 1 hour.

Example 2

The procedure of Example 1 was followed, using 2648 grams (2.04 moles)of 1300 molecular weight polyisobutene, 389.4 grams (4.08 moles) ofmaleic anhydride, 29.8 grams (0.204 mole) of di-t-butylperoxide, and 318grams of Chevron 100NR diluent oil. The resulting polyisobutenylsuccinic anhydride product had a saponification number of 63.8 mgKOH/gram of sample, 45 weight percent actives, and an average of 1.87succinic groups per polyisobutenyl group. The conversion ofpolyisobutene Was about 41.8 percent.

Example 3

The procedure of Example 1 was followed, using 2167 grams (1.67 moles)of 1300 molecular weight polyisobutene, 326.97 grams (3.34 moles) ofmaleic anhydride, 24.34 grams (0.167 moles) of di-t-butylperoxide, and260 grams of Chevron 100NR diluent oil. The resulting polyisobutenylsuccinic anhydride product had a saponification number of 63.8 mgKOH/gram of sample, 45 weight percent actives, and an average of 1.87succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 41.8 percent.

Example 4

The procedure of Example 1 was followed, using 1600 grams (1.23 moles)of 1300 molecular Weight polyisobutene, 193 grams (1.97 moles) of maleicanhydride and 28 grams (0.192 mole) of di-t-butylperoxide. In addition,300 grams of a C₉ aromatic solvent was used instead of the Chevron 100NRdiluent oil and the reaction time was 14 hours instead of 5 hours. Theresulting polyisobutenyl succinic anhydride product had a saponificationnumber of 84.2 mg KOH/gram of sample, 60.4 weight percent actives, andan average of 1.84 succinic groups per polyisobutenyl group. Theconversion of polyisobutene was about 57.3 percent.

Example 5

The procedure of Example 1 was followed, using 60,700 grams (46.7 moles)of 1300 molecular weight polyisobutene, 4,560 grams (46.7 moles) ofmaleic anhydride and 681.7 grams (4.67 moles) of di-t-butylperoxide. Nosolvent was used and the reaction time was 11 hours. The resultingpolyisobutenyl succinic anhydride product had a saponification number of46.5 mg KOH/gram of sample, 44.4 weight percent actives, and an averageof 1.34 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 42.0 percent.

Example 6

The procedure of Example 1 was followed, using 61,900 grams (47.6 moles)of 1300 molecular weight polyisobutene, 9,332.6 grams (95.2 moles) ofmaleic anhydride and 695.2 grams (4.76 moles) of di-t-butylperoxide. Nosolvent was used and the reaction time was 14 hours. The resultingpolyisobutenyl succinic anhydride product had a saponification number of94.5 mg KOH/gram of sample, 65.4 weight percent actives, and an averageof 1.92 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 62.3 percent.

Example 7

The procedure of Example 1 was followed, using 42,800 grams (19.5 moles)of a polyisobutene having a number average molecular weight of 2200 anda methylvinylidene isomer content of less than 2 percent, 4,294 grams(43.8 moles) of maleic anhydride and 523 grams (3.58 moles) ofdi-t-butylperoxide. No solvent was used and the reaction time was 14hours. The resulting polyisobutenyl succinic anhydride product had asaponification number of 41.7 mg KOH/gram of sample, 59 weight percentactives, and an average of 1.46 succinic groups per polyisobutenylgroup. The conversion of polyisobutene was about 57.5 percent.

COMPARATIVE EXAMPLES Comparative Example 1

This example follows the procedure of U.S. Pat. No. 3,367,864, ExampleI, part (1).

To a 2-liter 3-necked flask equipped with a thermometer, nitrogen inlet,condensor and stirrer was added 400.0 grams (0.355 mole) of apolyisobutene having a number average molecular weight of about 1100 anda methylvinylidene isomer content of about 2 percent, 38.27 grams (0.39mole) of maleic anhydride, 6.89 grams (0.047 mole) ofdi-t-butylperoxide, and 210 ml. of toluene as a solvent. This mixturewas stirred and heated at reflux (110° C.) for a period of 30 hours.Then the toluene was removed in vacuo, and the product was dissolved in250 ml. of hexane and filtered to remove the unreacted maleic anhydride.The hexane was then removed in vacuo. The resulting polyisobutenylsuccinic anhydride product had a saponification number of 29.2 mgKOH/gram of sample, 16.24 weight percent actives, and an average ofabout 2.09 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 14.1 percent. The half-life of thedi-t-butylperoxide free radical initiator at the reaction temperature of110° C. is about 120 hours.

Comparative Example 2

The procedure of Comparative Example 1 was repeated. The resultingpolyisobutenyl succinic anhydride product had a saponification number of7.7 mg KOH/gram of sample, 4.7 weight percent actives, and an average ofabout 1.87 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 4.1 percent.

Comparative Example 3

The procedure of Comparative Example 1 was followed, using 330 grams(0.35 mole) of a polyisobutene having a number average molecular weightof about 950 and a methylvinylidene isomer content of about 2 percent,32.3 grams (0.33 moles) of maleic anhydride, 5.8 grams (0.040 mole) ofdi-t-butylperoxide, and 210 ml. of toluene as a solvent. The resultingpolyisobutenyl succinic anhydride product had a saponification number of87.3 mg KOH/gram of sample, 48 weight percent actives, and an average ofabout 1.83 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 43.7 percent.

Comparative Example 4

The procedure of Comparative Example I was followed, using 390 grams(0.30 mole) of polyisobutene having a number average molecular weight ofabout 1300 and a methylvinylidene isomer content of about 6 percent,32.3 grams (0.33 mole) of maleic anhydride, 5.8 grams (0.040 mole) ofdi-t-butylperoxide, and 210 ml. of toluene as a solvent. The resultingpolyisobutenyl succinic anhydride product had a saponification number of53.9 mg KOH/gram of sample, 43 weight percent actives, and an average ofabout 1.63 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 40.2 percent.

Comparative Example 5

The procedure of Comparative Example 1 was followed, using 330 grams(0.35 mole) of 950 molecular weight polyisobutene, 32.3 grams (0.33 moleof maleic anhydride and 5.8 grams (0.040 mole) of di-t-butylperoxide. Inaddition, 210 ml. of xylene was used as a solvent instead of toluene andthe reaction temperature was 114° C. instead of 110° C. The resultingpolyisobutenyl succinic anhydride product had a saponification number of80.9 mg KOH/gram of sample, 43 weight percent actives, and an average ofabout 1.90 succinic groups per polyisobutenyl group. The conversion ofpolyisobutene was about 38.7 percent.

Comparative Examples 1-5 show that the use of a di-t-butylperoxideinitiator at the reaction temperature of 110° C. gives conversions ofonly 4.1 to 43.7 percent, even at the relatively long reaction time of30 hours.

Comparative Example 6

To a 2-liter flask equipped with a stirrer, thermometer and condensorwas added 384.6 grams (0.405 mole) of a polyisobutene having a numberaverage molecular weight of 950 and a methylvinylidene isomer content ofabout 2 percent, 119 grams 1.215 moles) of maleic anhydride and 250 ml.of toluene as a solvent. This mixture was heated to reflux (110° C.) andto this was added a total of 15.5 grams (0.081 mole) of alpha,alpha'-azo-bisisobutyronitrile (AIBN) over a period of four hours. Thereaction was heated for a total of six hours. The product was thencooled, placed into a separatory funnel and the top phase was separatedand filtered to remove excess maleic anhydride. The toluene was thenremoved in vacuo. The resulting polyisobutenyl succinic anhydrideproduct had a saponification number of 24.3 mg KOH/gram of sample, 13weight percent actives, and an average of 1.89 succinic groups perpolyisobutenyl group. The conversion of polyisobutene was about 11.1percent. The half-life of the AIBN free radical initiator at thereaction temperature of 110° C. is about 3 minutes. This example showsthat the use of a free radical initiator having a very short half-lifeat the temperature of reaction results in a low conversion ofpolyolefin.

What is claimed is:
 1. A process for the preparation of analkenyl-substituted succinic anhydride wherein the -alkenyl substituenthas a number average molecular weight of from about 500 to 5000 and theaverage number of succinic groups per alkenyl group is greater than 1.2which comprises reacting a polyolefin having an alkylvinylidene isomercontent of less than about 10 percent and a number average molecularweight of about 500 to 5000 with maleic anhydride in the presence of afree radical initiator at a temperature in the range of about 80° C. to220° C. for a period of less than 20 hours, wherein the molar ratio ofmaleic anhydride to polyolefin is about 1.0:1 to 9:1, and wherein thehalf-life of the decomposition of the free radical initiator is about 5minutes to 10 hours at the reaction temperature.
 2. The processaccording to claim 1, wherein the alkenyl succinic anhydride producedhas an average of at least about 1.3 succinic groups per alkenyl group.3. The process according to claim 2, wherein the alkenyl succinicanhydride produced has an average of about 1.3 to 4.0 succinic groupsper alkenyl group.
 4. The process according to claim 3, wherein thealkenyl succinic anhydride produced has an average of about 1.3 to 2.5succinic groups per alkenyl group.
 5. The process according to claim 1,wherein the polyolefin has a number average molecular weight of about700 to
 3000. 6. The process according to claim 5, wherein the polyolefinhas a number average molecular weight of about 900 to
 2500. 7. Theprocess according to claim 1, wherein the polyolefin is a polybutene orpolypropylene.
 8. The process according to claim 7, wherein thepolyolefin is a polyisobutene.
 9. The process according to claim 8,wherein the polyisobutene has a number average molecular weight of about900 to
 2500. 10. The process according to claim 10, wherein the freeradical initiator employed is a peroxide free radical initiator.
 11. Theprocess according to claim 10, wherein the peroxide free radicalinitiator is di-tert-butyl peroxide.
 12. The process according to claim1, wherein the molar ratio of maleic anhydride to polyolefin is about2:1 to about 4:1.
 13. The process according to claim 1, wherein thereaction is carried out at a temperature in the range of about 140° C.to about 180° C.
 14. The process according to claim 13, wherein thereaction is carried out at a temperature in the range of about 145° C.to about 165° C.
 15. The process according to claim 1, wherein thereaction is carried out for a period of about 1 to 15 hours.
 16. Theprocess according to claim 1, wherein the reaction is carried out in theabsence of a solvent.